Atmospheric corrosion phenomena under thin electrolyte films occur predominantly in the interior of aircraft during certain phases of flight or after landing. In this environment the temperature of the outer skin of the fuselage structure is as low as approximately −55° C., so that the components subjected to ambient temperatures cool correspondingly, and on the inside of the structure condensate and ice form, with the result that different metallic materials that are interconnected in an electrically conductive manner are subject to galvanic corrosion in the presence of an aqueous phase.
Up to now galvanic corrosion has been examined in that, for example, the substrate to be examined is cooled to a temperature below the dew point of the electrolyte so that on the substrate an electrolyte film forms that essentially comprises water. This process is associated with a disadvantage in that the film formation cannot be controlled with respect to the conductivity and composition of the electrolyte. After the electrolyte film has formed, uncontrollable and unavoidable evaporation of the film occurs so setting the film thickness is very sensitive to any changes in the ambient conditions, such as the temperature or relative atmospheric humidity. The condensation behavior and the film formation are a function of the thermal conductivity of the substrate or of the substrate combination as well as of the surface texture, and for this reason it is difficult to form a uniform film on a substrate comprising various materials.
In an alternative method the electrolyte film is formed on the substrate in that by means of a pipette a defined quantity of electrolyte that is required for a desired layer thickness is applied which is distributed more or less uniformly on the substrate surface. In this process the uniformity of the layer can only be assumed. Furthermore, as is the case in the above-mentioned method, uncontrollable evaporation effects will occur.